1. Field of the Invention
This invention relates to a plastic packaged semiconductor device, and more particularly to a multichip packaged semiconductor device having a plurality of LSI chips or discrete semiconductor elements transfer-molded in a single package and a method for manufacturing the same.
2. Description of the Related Art
In recent years, considerable attention has been paid to a multichip packaged semiconductor device having a plurality of LSI chips or discrete semiconductor elements which are molded in a single package having a particular shape or the same shape as that of a standard integrated circuit device in order to enhance the density and miniaturize the semiconductor device. The packaged semiconductor device is briefly called a multichip package (MCP), and it can be used in combination with the conventional LSI chips or discrete semiconductor elements and the conventional manufacturing device and testing device for effecting the LSI manufacturing process and testing process can be used. Therefore, the turn around time (TAT) taken for forming a plurality of integrated circuits into one chip when developing new integrated circuits can be made short and the development cost can be made low. Further, since the conventional LSIs and discrete semiconductor devices are used, the package can be dealt with in the same manner as in the prior art case. In addition, in the MCP, it is only required to newly develop lead frames, and since the outer lead section having the same shape as that arranged in the package line-up can be used, it is only necessary to design the inner lead section of the lead frame. For this reason, the package is suitable for the custom IC, and the custom IC can be manufactured in a shorter TAT than in a case wherein a hybrid IC or the like is manufactured.
The inventor of this application developed the technique of manufacturing multichip packaged semiconductor devices by mounting a plurality of LSI chips or discrete semiconductor elements on a lead frame and sealing them into a single packaged by the transfer molding and commercialized the multichip packaged semiconductor devices. The multichip packaging technique is disclosed in detail in "NIKKEI MICRODEVICES" 1989 February, pp. 95 to 101 a thesis written by the inventor and some of his colleagues. Further, the inventor of this application filed a U.S. patent application (U.S. patent application Ser. No. 07/506,251) relating to the multichip packaging techniques and received an allowance thereof of Aug. 9, 1991.
As the integration density of the semiconductor device such as IC or LSI becomes higher, the number of electrode pads for supplying input signals and power source voltages or outputting output signals is increased, the power consumption is also increased, and the operation speed is made higher. When the electrode pads connected to bonding wires are arranged at a higher density on a chip with an increase in the integration density of the semiconductor device, the bonding tool will come into contact with adjacent bonding wires at the same time, thereby making it impossible to attain correct bonding. Further, since the size of the electrode pad and the electrode pad pitch cannot be made less than a certain value even if the semiconductor elements can be miniaturized, the chip size comes to have a limitation and the signal wiring length cannot be reduced on the chip.
In order to solve the above problem, the tape automated bonding (TAB) technique using a tape carrier is proposed. The TAB technique is a method effected by forming a device hole in a long flexible resin film, disposing metal wirings formed of a plurality of leads around the device hole, and connecting the metal wirings to electrode pads of the chip via the projected electrodes (bumps) and it may be applied to a semiconductor device such as a GaAs integrated circuit which requires a high operation speed. The TAB technique is described in detail in the article by KENZO HATADA, MATSUSHITA Electric Industrial Co. "Introduction of TAB Technique" published from Industrial Research Committee, for example.
However, in the semiconductor device formed by using the TAB technique, it is possible to derive out electrodes from discrete chips, but since it is impossible to constitute circuits by making use of a plurality of chips, it cannot be applied to the MCP type semiconductors device described above. Further, since the tape carrier is not formed of material such as a lead frame with high heat conductivity and the thermal resistance is large and heat radiation efficiency is low, a severe limitation is imposed on the type of semiconductor device in which the TAB technique can be used. In addition, since the outer lead is mechanically weak, it becomes impossible to wrap the same after it is separated from the tape carrier, and it becomes necessary to prepare a specified mounting device on the user's side, thus lowering the flexibility thereof and raising the cost of the instrument using the TAB package.
Further, a technique for connecting an electrode pad of a chip to an inner lead section of a lead frame by use of the above TAB technique is disclosed in Japanese Patent Disclosure No. 2-121343. By using technique disclosed in the above Japanese Patent Disclosure, some of the defects associated with the TAB technique can be eliminated, but the above Japanese Patent Disclosure discloses or suggests nothing about the application of the technique to the MCP type semiconductor device.
SUMMARY OF THE INVENTION p Accordingly, a first object of this invention is to provide a multichip packaged semiconductor device which can be mounted at a high density and a method for manufacturing the same.
A second object of this invention is to provide a multichip packaged semiconductor device which has a small thermal resistance and a high heat radiation efficiency and which can be applied to various types of semiconductor devices and a method for manufacturing the same.
A third object of this invention is to provide a multichip packaged semiconductor device which does not require use of a special mounting device on the user's side, which is highly flexible and which will not increase the cost of an instrument using the semiconductor device and a method for manufacturing the same.
A fourth object of this invention is to provide a multichip packaged semiconductor device which can be hermetically sealed and is highly reliable and a method for manufacturing the same.
A fifth object of this invention is to provide a multichip packaged semiconductor device in which the wiring can be made short so as to reduce the impedance component of the wiring and the electrical characteristics such as the operation speed can be improved and a method for manufacturing the same.
The above first to fifth objects of this invention can be obtained by a semiconductor device comprising a lead frame having an inner lead section, an outer lead section and at least one island; a plurality of semiconductor chips formed on the island of the lead frame and each having an electrode pad and each having at least one semiconductor element formed therein; and a flexible resin tape having device holes formed in positions corresponding to mounting sections of the semiconductor chips and having a wiring pattern for electrically connecting the electrode pads of the semiconductor chips to the inner lead section of the lead frame.
Further, the above first to fifth objects of this invention can be attained by a semiconductor device manufacturing method comprising the steps of mounting a plurality of semiconductor chips on at least on island formed on a lead frame; disposing a flexible resin tape having a wiring pattern and a plurality of device holes on the lead frame; connecting one end of the wiring pattern formed on the flexible resin tape to electrode pads formed on the plurality of semiconductor chips; and connecting the other end of the wiring pattern formed on the flexible resin tape to an inner lead section of the lead frame.
Since leads of the inner lead section of the lead frame and the electrode pads formed on the semiconductor chips are connected by means of the wiring pattern formed on the flexible resin tape, the mounting can be effected at a higher density than in a case wherein the connection is made by use of the wire bonding. Further, since a circuit can be constructed by use of a plurality of semiconductor chips by connecting a plurality of semiconductor chips to one another via the wiring pattern formed on the flexible resin tape, a plastic packaged semiconductor device for the MCP can be realized by use of the TAB technique. A plurality of semiconductor chips are mounted on a plurality of islands formed of material with high heat conductivity so that the thermal resistance can be reduced, the heat radiation efficiency can be enhanced and the limitation imposed on the type of applicable semiconductor devices can be alleviated. Since the lead frame is used and the mechanical strength of the outer lead section is higher than in a case wherein the TAB technique is used, it becomes unnecessary to use a special mounting device on the user's side, the flexibility can be enhanced and the cost of an instrument using the semiconductor device will not be raised. The semiconductor chips are transfer-molded in a resin package so that the excellent hermetic sealing can be attained and the reliability thereof can be made high. Further, since a plurality of semiconductor chips can be connected together in substantially the linear form via the wiring pattern formed on the flexible resin tape, the wiring can be made short so as to reduce the impedance component and the electrical characteristic such as the operation speed can be enhanced.
Thus, according to this invention, a multichip packaged semiconductor device which can be mounted at a high density and a method for manufacturing the same can be provided and can be widely used in the industrial-consumer field.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.